Chambord, I'm about a mile out of Oswestry, send me a PM if you fancy heading over to check it out, you're more than welcome.
re the seatpost joint, there needs to be a weld for structural rigidity, without it the frame would be a little flexy side to side. The idea behind the twin top tube is one of strength, all forces are transferred the full length of the bike and not to a junction, this also results in the bike being noticeably more comfortable. It's quite complex to get it right, plus I think it looks great.
re seatpost size, frame runs a 27.2 post. This is the only acceptable size if you plan on using a regular post on a hardtail. The ethos of the bike is all about getting away from technology, though I have to admit dropper posts are great. I work in a trail centre (llandegla) and we see a lot of dropper posts coming back with problems. Thompson are about to release a 27.2 dropper which is of amazing quality. X-fusion also make a hydraulic one that works as well as anything on the market.
re cable guides - the ones in the picture were put on the wrong side and were for a front mech or dropper post. I'd been toying with the production frame being 1x10 specific but the overwhelming feedback I've had is that it should be SSable. At tis stage I think I'd be daft not to cover all options. In future, and depending on demand, I think i'll offer the frame 3 ways.
Hope all this helps, and thanks for your interest. cheers, Andy